Insects on lodgepole pine in Sweden — current knowledge and potential risks

Insects on lodgepole pine in Sweden Ð current knowledge andpotential risks

AÊ ke LindeloÈw*, Christer BjoÈrkmanDepartment of Entomology, Swedish University of Agricultural Sciences, P.O. Box 7044, S-75007 Uppsala, Sweden

Accepted 2 January 2000

Abstract

Eighty species of forest insects have thus far been recorded feeding on lodgepole pine in the Nordic countries (61 in

Sweden). The list includes species that have Scots pine as their main host and which feed on needles, ¯owers, cones, and

shoots, as well as species boring in the phloem and xylem of dead or dying Norway spruce. Contrary to our expectations, most

of the insect species that have colonised lodgepole pine in Sweden can be considered specialists (with regard to host plant

range and feeding mode) rather than generalists. We suggest that the current dominance of specialised insect herbivores is

related to the similarity in chemistry and morphology between lodgepole and Scots pine.

Only a few of the species considered to be pests have caused considerable damage in lodgepole pine stands in the Nordic

countries. The most severe damage has been caused by the needle feeders Neodiprion sertifer and Anthonomus phyllocola.

Hylobius abietis, the most harmful forest insect species in Scandinavia, attacks lodgepole pine seedlings to about the same

degree as it attacks Scots pine and Norway spruce and causes similar levels of mortality. Other pest species reported to have

caused considerable damage to lodgepole pine are Pissodes validirostris (cones) and Rhyacionia bouliana (shoots).

No insect species native to North America and living on lodgepole pine have yet to become established in the Nordic

countries since the introduction of this exotic tree species. The risk of large-scale damage in Sweden is discussed in relation to

the distribution and management of lodgepole pine. # 2001 Elsevier Science B.V. All rights reserved.

Keywords: Pinus contorta; Lodgepole pine; Insect herbivores; Forest pest insects

1. Introduction

The area planted with lodgepole pine (Pinus con-

torta var. latifolia) in Sweden has reached roughly

600 000 ha, almost all of it situated north of 608N.

However, a number of older and mostly small experi-

mental stands established at the beginning of this

century are scattered over the country. Our knowledge

concerning the occurrence of indigenous insects

on lodgepole pine and the damage they cause is

based on observations made in provenance trials

(RemroÈd, 1963; Ingerstedt, 1966; Hagner and Fahl-

roth, 1974; Krutzsch, 1974), reports from foresters and

a few studies aimed speci®cally at assessing the

performance of certain insect species on this new host

tree (Eidmann, 1982; Annila et al., 1983; LindeloÈw

and Iacobaeus, 1985; Olofsson, 1989; BjoÈrkman,

1997). However, no systematic studies have been

made on the occurrence of insects on lodgepole pine

in Sweden.

In this paper we summarise the knowledge on

insect species observed feeding on lodgepole pine

Forest Ecology and Management 141 (2001) 107±116

* Corresponding author.

E-mail address: [email protected] (AÊ . LindeloÈw).

0378-1127/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.

PII: S 0 3 7 8 - 1 1 2 7 ( 0 0 ) 0 0 4 9 4 - 1

in Sweden. The list presented is complemented with

observations from other Nordic countries. In addition,

experiences gained in other European countries where

lodgepole pine has been grown under similar climatic

conditions are considered. One main objective of this

survey was to create a platform for assessing the risk

of future insect outbreaks in lodgepole pine stands in

Sweden. For this reason, we have tried to take into

account all relevant factors in this regard, such as host

tree properties, silvicultural practices and uninten-

tional introductions of insects accompanying imported

seeds, grafts or timber from abroad. Furthermore, we

have tried to discern patterns concerning the type of

insects that have colonised lodgepole pine thus far and

have compared these patterns with those found for

other exotic plant species.

2. The host and silviculture practices

Lodgepole pine is widely distributed in the USA

and Canada, where it is comprised of different sub-

species and a large variety of provenances (Edwards,

1954). In this region lodgepole pine serves as a host

tree for more than 300 species of insects (Lindgren,

1980). Some of these species, such as the mountain

pine beetle (Dendroctonus ponderosae), are consid-

ered to be among the most devastating forest pest

species in the world (Safranyik et al., 1974).

Within the genus Pinus, lodgepole pine is distantly

related to the native Scots pine (Pinus sylvestris L.)

(see Mirov, 1967). Characteristics such as growth rate,

¯owering, chemical properties and bark structure

differ considerably from those of Scots pine (Annila

and Hiltunen, 1977).

Since the time of the ®rst large-scale introduction of

lodgepole pine into Sweden in the 1960s there has

been a successive shift in favour of more northerly

provenances in order to meet the need for greater

hardiness in some of the target areas (Lindgren et al.,

1993).

Swedish forestry law stipulates that lodgepole pine

may only be planted in areas north of the 598300

latitude in western Sweden and 608000 in eastern

Sweden. One reason for this restriction was the pre-

sumed increased risk for insect damage south of these

latitudes. In some regions in mid-Sweden, lodgepole

pine accounts for more than 5% of the forest area

(Segebaden, 1993).

3. Patterns at the community level

At present, 61 species of indigenous forest insects

have been observed feeding on lodgepole pine in

Sweden. An additional 20 species, likely to occur on

lodgepole pine in Sweden but hitherto only recorded

from lodgepole pine in Finland or Denmark, are also

listed (see Appendix A). The list includes species from

the insect orders Heteroptera/Homoptera, Coleoptera,

Hymenoptera, Lepidoptera and Diptera.

When a plant species is introduced into a new

environment it will be colonised by insects. Such

colonisation is typically asymptotic; i.e. initially there

is a rapid increase in the number of species, but the rate

at which species are added decreases gradually

(Strong et al., 1984). A number of factors determine

which insect species will be recruited and their colo-

nisation rates (e.g. Connor et al., 1980; Tahvanainen

and NiemilaÈ, 1987). We will compare some of the

patterns found in previous studies with those found

here and brie¯y speculate as to the processes that

could be responsible for these patterns.

The most striking pattern is that the herbivorous

(needle-, bud-, ¯ower- and cone-feeding) insect spe-

cies that have colonised lodgepole pine in Sweden

come from Scots pine, whereas the saproxylic (feed-

ing on the phloem and xylem of dying or dead trees)

ones come from Norway spruce (Picea abies Karst.).

This pattern is probably due to the speci®c chemical

and morphological properties of the different types of

plant tissues in these three conifer species. This could,

thus, be viewed as one out of many examples support-

ing Janzen's statement that `̀ herbivores do not eat

Latin binomials'' (Janzen, 1979). In other words, for

successful colonisation it is more important that (1)

the insect recognises the tissue as food and (2) is

capable of processing the tissue physiologically. (3)

The likelihood of an introduced plant being a suitable

host is greater if it is taxonomically closely related to

the native host. This phenomenon is exempli®ed by

the fact that a large number of the insect species which

have colonised lodgepole pine in Britain stem from

moorland plants from the families Myricaceae and

108 AÊ . LindeloÈw, C. BjoÈrkman / Forest Ecology and Management 141 (2001) 107±116

Ericaceae (Winter, 1974) (also see the discussion

below concerning specialists versus generalists).

The time available for colonisation is important,

and it has been argued that insects feeding within

plant tissue (endophagous) should colonise a newly

introduced host more slowly than externally feeding

insects (Strong et al., 1984). However, among the

herbivorous insects that have colonised lodgepole

pine the opposite relation was found: The proportion

of species recruited was highest for shoot- and bud-

boring insects, lowest for externally feeding species

and intermediate for mining insects (Fig. 1). Because

the number of species was low in the group with

shoot- and bud-boring insects, a statistical comparison

was only made between the mining and chewing

insects. This comparison revealed, however, that

the two groups did not differ signi®cantly with respect

to the proportion of the species from Scots pine

that have colonised lodgepole pine (X2�0.81,

p>0.1, d.f.�1).

There are some potential problems with using the

number of species as independent observations in

statistical analyses. For example, there is always a

risk that most or all species with a given trait stem

from a common ancestor, therefore overestimating the

importance of the number of species observed. Thus,

the results of our comparisons should be interpreted

with caution. Nevertheless, as this is the only method

available, we have used it in the hopes of ®nding

patterns worth pursuing in future studies. The com-

parisons are based on information from the Appendix

A for lodgepole pine and from BjoÈrkman and Larsson

(1991) for Scots pine.

It is commonly the case that generalistic insect

species colonise introduced plants faster compared

with more specialised ones, probably because species

that are too specialised may have problems in colonis-

ing a new plant species (Goeden and Ricker, 1968;

Root and Tahvanainen, 1969; Goeden, 1971, 1974;

Wheeler, 1974). This was not the pattern found

for insects that have colonised lodgepole pine in

Sweden. To the contrary, monophagous (i.e. feeding

on plants from one genus) lepidopteran species

have colonised lodgepole pine to a greater extent,

in terms of both number of species and proportion

of the pool, compared with species with broader

host plant ranges (Fig. 2). The same trend was found

when comparing insect groups with broader host

ranges: both the number and proportion of colonising

species was greater for oligophagous (i.e. feeding

on plants from several genera) insects compared

with polyphagous ones (i.e. feeding on plants from

more than one family) (Fig. 2). There was a signi®cant

difference between monophagous, oligophagous

and polyphagous lepidopteran species with respect

to the proportion of the species in the pool that

had colonised lodgepole pine (X2�7.07, p<0.05,

d.f.�2). A similar pattern was found for the saw¯ies,

Fig. 1. Proportion of species in the pool of Lepidopterans on

P. sylvestris (native to Sweden) that have colonised the exotic

P. contorta (native to North America), calculated for each of the

three main feeding guilds (Appendix A and from BjoÈrkman and

Larsson, 1991).

Fig. 2. Number of Lepidoptera species feeding on the native Scots

pine and exotic lodgepole pine in Sweden (Appendix A and

BjoÈrkman and Larsson, 1991).

AÊ . LindeloÈw, C. BjoÈrkman / Forest Ecology and Management 141 (2001) 107±116 109

even though all species in the pool are monophagous

(BjoÈrkman and Larsson, 1991); i.e. a very high

proportion (11 out of 13) has colonised lodgepole

pine.

There could be several reasons to explain why,

contrary to expectation, specialised insects have colo-

nised lodgepole pine in greater numbers and more

quickly compared with more generalised ones. One

possibility could be that for the specialised insects

concerned, lodgepole pine and Scots pine are fairly

similar in terms of their chemistry and morphology,

implying a close relation between the two pine

species.

In Britain, into which lodgepole pine also has

been introduced, the pattern of colonisation of lepi-

dopterans was different (Winter, 1974), with poly-

phagous species outnumbering monophagous ones.

The reason for this apparent discrepancy between

Britain and Sweden could partly be due to the fact

that Winter (1974) compared numbers of species

rather than proportions. However, even when we

used species number in our analysis, monophagous

species still dominated over oligophagous and poly-

phagous ones. Another factor that differs between

Britain and Sweden is the availability of insect

individuals in the pool (size of the insect pool avail-

able). The area planted with Scots pine in Britain

is much smaller than the area planted in Sweden.

Thus, the number of colonisation events (i.e. an insect

from Scots pine moving over to lodgepole pine)

should have been much lower in Britain than in

Sweden.

As in most other cases with introduced plants, we

know very little about herbivore abundance. The level

of herbivory may be independent of the number of

insect species. In one of the few studies on this topic it

was shown that levels of herbivory were similar on

introduced and native tree species in Britain, even

though fewer species colonised the introduced ones

(Yela and Lawton, 1997).

4. For better or for worse: examples of lodgepolepine being a bad and a good host

Although similar numbers of saproxylic species live

on Scots pine and Norway spruce many of the species

living on spruce are found on dead lodgepole pine

trees. Among these species there are some obvious

examples of old world insects which have not evolved

sympatrically with this new host tree. For example,

although the bark beetle Pityogenes chalcographus

colonises non-resistant lodgepole pine stems, e.g.

felled by non-commercial thinning, reproduction in

such stems is often very low (LindeloÈw and Iacobaeus,

1985, LindeloÈw, unpublished). The reason for the

beetle's poor performance in lodgepole pine is not

known.

Another well-known example is Pissodes validi-

rostris. The females lay their eggs in the cones, and

often the numbers of eggs and larvae are higher in

lodgepole pine cones, implying a higher degree of

intraspeci®c larval competition. Although the emer-

ging young adults have dif®culties boring through the

hard, serotinous cones (Annila, 1975), on average,

more adults emerge from lodgepole pine cones than

from Scots pine cones. The lower content of alpha-

pinene in the cones of lodgepole pine may explain

their greater susceptibility to damage caused by the

pine cone weevil.

On the other hand, some species seem to ®nd

lodgepole pine to be an optimal host. For example,

in Anthonomus phyllocola, larvae develop in the male

¯owers, and adults can frequently be found feeding on

current-year foliage in stands 10 years old and older. It

is believed that the larger male ¯owers and earlier

¯owering of lodgepole pine favour the growth of A.

phyllocola populations, explaining why this species is

one of the most characteristic forest insects in lodge-

pole pine stands in Sweden (LindeloÈw, 1990; Petters-

son, 1992).

The possible occurrence of sympatric speciation

cannot be excluded in areas where lodgepole pine

is the dominating tree species. Among other insects,

gall midges mining in the needles seem to ful®l

the criteria for this process (Glynn, personal commu-

nication).

5. Reduced growth caused by defoliation

Some indigenous herbivores, i.e. one diprionid

species and one species of curculionid, attack lodge-

pole pine frequently and cause heavy defoliation

from time to time. Outbreaks of the European Pine

Saw¯y (N. sertifer) often occur in Scots pine and

110 AÊ . LindeloÈw, C. BjoÈrkman / Forest Ecology and Management 141 (2001) 107±116

lodgepole pine stands in Sweden, Norway and

Finland (Christiansen, 1970; AustaraÊ et al., 1983).

Generally, the trees recover after a period of reduced

growth, and few trees are killed (AustaraÊ et al., 1983).

Signs of maturation feeding by newly emerged

adults of A. phyllocola on current-year needles in

late June can often be seen in lodgepole pine stands

but the impact of such feeding on growth is unknown.

Occasionally N sertifer, which feeds on older foliage,

and A. phyllocola, which feeds on current-year nee-

dles, reach outbreak levels simultaneously and may

cause complete defoliation for a couple of years.

Trees in seed orchards are sometimes treated with

insecticides to prevent repeated defoliation by these

two species.

6. Tree mortality caused by insects

Insects have only occasionally caused severe tree

mortality in lodgepole pine stands in Sweden. On the

other hand, the fungal pathogen Gremmeniella abie-

tina has killed large numbers of young trees in north-

ern Sweden (Karlman et al., 1994).

Larvae of the highly polyphagous curculionid

Otiorhynchus dubius once killed more than

1 000 000 seedlings in a nursery. The Black Army

Cutworm (Actebia fennica) considered to be quite

rare in Sweden, more or less totally destroyed a

young plantation in 1976 (EhnstroÈm, 1985). In North

America, damage caused by this caterpillar is com-

mon (Amman and Safranyik, 1985). Feeding by pine

weevils (Hylobius spp.) causes heavy mortality every

year in young coniferous plantations, mainly in south-

ern Sweden (Ollas, 1992). Although there are no

mortality data for lodgepole pine plantations, for

the country as a whole pine weevil damage is gen-

erally low because it declines to the north where most

lodgepole pine is planted. Lodgepole pine seedlings

seem to be as attractive as food source as Scots pine

seedlings for pine weevils (Annila et al., 1983; Lin-

deloÈw, 1975).

On rare occasions the spruce bark beetle (Ips typo-

graphus) has attacked and killed trees in older stands

in Norway and Denmark (LoÈyttyniemi et al., 1979;

AustaraÊ et al., 1983). Attacks by P. chalcographus

in younger stands have been frequently reported

(EhnstroÈm, 1985).

7. Other kinds of damage

Extensive malformations of current-year shoots

caused by the larvae of the European pine shoot moth

(Rhyacionia buoliana) tunnelling in the core have

been observed in Denmark (Esbjerg and Feilberg,

1971; Bejer-Petersen, 1972; Zethner and Bejer-Peter-

sen, 1972) as well as in Sweden, mainly in the south

(Eidmann, 1982).

Although severe damage caused by the indigenous

pine cone weevil P. validirostris has been reported in

lodgepole pine cones in Finland (Annila, 1975), no

such damage has yet occurred in Swedish seed orch-

ards (Eidmann, 1982). Feeding by the larvae in cones

reduces seed production.

8. Indigenous insect species and the risk foroutbreaks

Many herbivorous insects known to reach outbreak

levels more or less regularly in central Europe seldom

cause problems in Sweden, e.g. the nun moth Lyman-

tria monacha, the pine tree lappet Dendrolimus pini,

the pine looper Bupalus piniaria, and the pine beauty

moth Panolis ¯ammea (Lekander, 1950, 1954; Chris-

tiansen, 1970; EhnstroÈm et al., 1974; LoÈyttyniemi

et al., 1979; AustaraÊ et al., 1983). Known outbreaks

of these species have been more or less con®ned to the

climatically favourable region of southern Sweden

where lodgepole pine is not allowed as a commercial

tree species.

On certain types of sites lodgepole pine may be

more likely to sustain serious damage by insect spe-

cies favoured by the site conditions. For example, the

pine beauty moth is currently damaging lodgepole

pine stands growing on peat in Scotland (Watt and

Leather, 1988), although this species has not damaged

its original host Scots pine in the area. Corresponding

phenomena have not yet been observed in Sweden

although N. sertifer, which is known to be favoured by

certain types of sites (Larsson and Tenow, 1984), often

reaches outbreak levels in lodgepole pine stands

(Olofsson, 1989). At the moment defoliation by N.

sertifer seems to be the most serious kind of insect

damage on lodgepole pine. N. sertifer can be espe-

cially damaging when defoliation by A. phyllocola or

gall midges occurs at the same time.

AÊ . LindeloÈw, C. BjoÈrkman / Forest Ecology and Management 141 (2001) 107±116 111

The high incidence of N. sertifer outbreaks in

lodgepole pine stands may to some extent be due to

the low concentration of resin acids (diterpenoids) in

the needles (BjoÈrkman, 1997). However, adult saw-

¯ies that have fed on Scots pines low in resin acids lay

more eggs than those that have fed on Scots pines rich

in resin acids, whereas the opposite seems to be the

case for lodgepole pine (Larsson et al., 1993). The fact

that the relationship between resin acid concentration

and fecundity seems to be positive instead of negative

in lodgepole pine (BjoÈrkman, 1997) calls for a more

comprehensive analysis of how this may affect the risk

for outbreaks.

9. Risk for unintentional introductions of harmfulinsects from North America

In North America, 35 species of insects are con-

sidered as pests or potential pests on lodgepole pine

(Amman and Safranyik, 1985). No insect species

native to North America and living on lodgepole pine

has yet been found in Sweden except on boats contain-

ing timber inspected in Swedish harbours. Neverthe-

less, some of the insects species on lodgepole pine in

Sweden are either circumpolar, such as the Black

Army Cutworm (A. fennica), a well-known pest spe-

cies, or introduced into North America, such as the

European Pine Shoot Moth (Rhyacionia buoliana)

(Evans, 1983).

Bejer (1981) cautioned that insects from North

America and East Asia, including Japan, pose a

potential risk in Sweden since these regions have

climatic conditions and conifer ¯oras similar to those

in Sweden. Small cone and seed insects as well as

aphids, seem to be most successful in following their

host trees. Saproxylic insects, on the other hand, rarely

succeed in establishing themselves in the absence of

suitable breeding substrate. However, nowadays tim-

ber is frequently imported into Sweden, both from

European and transatlantic countries, e.g. Chile

(Schroeder, 1990). Many foreign species of saproxylic

forest insects have been found in timber in Swedish

harbours (AustaraÊ et al., 1983). And recently the

ambrosia beetles Xylosandrus germanus and Gnato-

trichus materiarius, originating from North America,

have been found in Sweden and Finland, respectively

(Lundberg, personal communication; Valkama et al.,

1998). At the moment importation of untreated soft-

wood from North America is prohibited because of the

risk of introducing the pine wood nematode (Bursa-

phelencus xylophilus) (Schroeder, 1990).

The number of exotic species accidentally intro-

duced into a region where they subsequently became

established as serious pests is much larger for North

America than for Europe (e.g. Mattson et al., 1994).

In some cases these species have caused severe

damage to indigenous tree species that were not

among its original hosts. Such is the case with the

balsam woolly aphid (Adelges piceae) which is now a

serious pest on native North American ®rs (Gibbs

and Wainhouse, 1986). It is, of course, dif®cult to

predict whether an introduced species will change

from a non-pest to a pest insect or vice versa when

faced with either its original host or an indigenous

new host species.

10. Conclusions

� Among the insect species that have colonised lod-

gepole pine in Sweden specialists outnumber gen-

eralists.

� No major insect damage has yet to occur on lodge-

pole pine in Sweden.

� The risk for sustaining severe insect damage over

large areas will probably remain low if reforestation

with lodgepole pine is allowed only north of the

608N latitude.

� In view of the strong restrictions on the importation

of seed, grafts and wood from North America, the

risk of unintentional introductions of insects should

be considered low.

� The large-scale introduction of lodgepole pine into

Sweden offers a good, but hitherto more or less

unexploited, opportunity for learning more about

how the introduction of a plant species affects insect

colonisation, insect species richness (biodiversity),

the composition of insect communities and insect

population dynamics (e.g. the risk for outbreaks).

Acknowledgements

We thank Mats W. Pettersson and Martin Schroeder

for helpful comments on the manuscript.

112 AÊ . LindeloÈw, C. BjoÈrkman / Forest Ecology and Management 141 (2001) 107±116

Appendix A

Species likely to occur on lodgepole pine in Sweden (Table 1).

Table 1

Host plants (main host genus), host range and kind of tissue utilised by the larvae and imagines of insect species/genera recorded on Pinus contorta in the Nordic

countriesa

Insect order/family Host Host rangeb Tissue Pest Status References

Larvae/imago On lodgepole On Scots

or spruce

Heteroptera

Aradus cinnamomeus Panz. Pinus Oligophagous Xylem/xylem Indifferent Major EhnstroÈm et al. (1974)

Homoptera

Pineus pini L. Pinus Monophagous Phloem/phloem Minor Major Krutzsch (1974)

Schizolachnus pineti (F.) Pinus Monophagous Needles/needles Indifferent Indifferent LindeloÈw (unpublished)

Coleoptera

Anthaxia quadripunctata (L.) Pinus, Picea Oligophagous Phloem/pollen Indifferent Indifferent LindeloÈw (unpublished)

Ernobius nigrinus (Sturm) Pinus Monophagous Xylem/± Indifferent Indifferent Karlman et al. (1994)

Rhagium inquisitor (L.) Pinus, Picea Polyphagous Phloem/± Indifferent Indifferent LindeloÈw (1975)

Tetropium sp. Picea, Pinus Oligophagous Phloem/± Indifferent Minor

Molorchus minor (L.) Picea, Pinus Oligophagous Phloem/± Indifferent Indifferent LindeloÈw (1975)

Monochamus sutor (L.) Picea, Pinus Oligophagous Phloem/phloem Indifferent Major LindeloÈw (1975)

Pogonocherus fasciculatus (DeG.) Pinus, Picea Oligophagous Phloem/± Indifferent Indifferent Arvidsson (1988)

Acanthocinus aedilis (L.) Pinus Oligophagous Phloem/± Indifferent Indifferent LindeloÈw (1975)

Cryptocephalus pini (L.) Pinus Oligophagous Debris/needles Indifferent Minor Annila et al. (1983)

Calomicrus pinicola (Duft.) Pinus Oligophagous Grassroots/needles Indifferent Minor Annila et al. (1983)

Otiorhynchus nodosus (MuÈller) Pinus, Picea, others Polyphagous Roots/needles Major Major

Brachyderes incanus (L.) Pinus Oligophagous Roots/needles Indifferent Minor LindeloÈw (unpublished)

Strophosoma capitatum (DeG.) Pinus, Picea, others Polyphagous Roots/needles Major Major LindeloÈw (1975)

Ankhonomus phyllocola (Herbst) Pinus Oligophagous Flower/Needles Major Indifferent

Bmconyx pineti (Payk.) Pinus Monophagous Needles/needles Indifferent Minor LindeloÈw (unpublished)

Magdalis frontalis (Gyll.) Pinus, Picea Oligophagous Xylem/phloem Indifferent Indifferent LindeloÈw (unpublished)

Magdalis violacea (L.) Pinus, Picea Oligophagous Xylem/phloem Indifferent Indifferent Annila et al. (1983)

Magdalis duplicata Germ. Pinus, Picea Oligophagous Xylem/phloem Indifferent Indifferent Annila et al. (1983)

Hylobius abietis (L.) Pinus, Picea Polyphagous Phloem/phloem Major Major RemroÈd (1963)

Pissodes pini (L.) Pinus Oligophagous Phloem/phloem Minor Minor LindeloÈw (unpublished)

Pissodes castaneus (DeG.) Pinus Oligophagous Phloem/phloem Indifferent Minor

Pissodes validirostris (Sahlb.) Pinus Monophagous Cones/phloem Major Minor Annila (1975)

Tomicus minor (Hartig) Pinus Oligophagous Phloem/xylem Indifferent Major

Tomicus piniperda (L.) Pinus Oligophagous Phloem/xylem Indifferent Major LindeloÈw (1975)

Dendroctonus micans (Kug.) Picea, Pinus Oligophagous Phloem/Phloem Minor Minor

Hylorgops glabratus (Zett.) Picea Oligophagous Phloem/phloem Indifferent Indifferent LindeloÈw (unpublished)

Hylorgops palliatus (Gyll.) Picea, Pinus Oligophagous Phloem Indifferent Indifferent LindeloÈw (1975)

Hylastes brunneus Er. Pinus Oligophagous Phloem/phloem Indifferent Minor LindeloÈw (unpublished)

Hylastes opacus Er. Pinus Oligophagous Phloem/phloem Indifferent Indifferent LindeloÈw (unpublished)

Polygraphus punctifrons Thoms. Picea Oligophagous Phloem/phloem Indifferent Indifferent Eidmann (1982)

Polygraphus poligraphus (L.) Picea Oligophagous Phloem/phloem Minor Major AustaraÊ et al. (1983)

Crypturgus pusillus (Gyll.) Picea, Pinus Oligophagous Phloem/phloem Indifferent Indifferent

Drupocoetes autographus (Ratz.) Picea Oligophagous Phloem/phloem Indifferent Indifferent Eidmann (1982)

Dryocoetes hectographus Reitt. Picea Oligophagous Phloem/phloem Indifferent Indifferent LindeloÈw (unpublished)

Cryphalus abietis (Ratz.) Picea, Pinus Oligophagous Phloem/phloem Indifferent Indifferent LindeloÈw (unpublished)

Trypodendron lineatum (Oliv.) Picea, Pinus Polyphagous Fungi/fungi Indifferent Major LindeloÈw (unpublished)

Pityogenes chalcographus (L.) Picea Oligophagous Phloem/phloem Minor Major LindeloÈw and

Iacobaeus (1985)

AÊ . LindeloÈw, C. BjoÈrkman / Forest Ecology and Management 141 (2001) 107±116 113

Table 1 (Continued )

Insect order/family Host Host rangeb Tissue Pest Status References

Larvae/imago On lodgepole On Scots

or spruce

Pityogenes quadridens (Hartig) Pinus Oligophagous Phloem/phloem Indifferent Indifferent LindeloÈw (1975)

Pityogenes bidentatus (Herbst) Pinus Oligophagous Phloem/phloem Indifferent Indifferent LindeloÈw (1975)

Ipstypographus (L.) Picea Oligophagous Phloem/phloem Minor Major LindeloÈw and

Iacobaeus (1985)

Ipstuplicatus (Sahlb.) Picea Oligophagous Phloem/phloem Indifferent Indifferent Annila et al. (1983)

Ipsamitinus (Eichh.) Picea Oligophagous Phloem/phloem Indifferent Indifferent

Orthotomicus proximus (Eichh.) Pinus Oligophagous Phloem/phloem Indifferent Indifferent

Orthotomicus suturalis (Gyll.) Pinus Oligophagous Phloem/phloem Indifferent Indifferent

Orthotomicus laricis (F.) Pinus Oligophagous Phloem/phloem Indifferent Indifferent

Hymenoptera

Acantholyda hieroglyphica Chr. Pinus Monophagous Needles/± Minor Minor

Urocerus gigas L. Picea, Pinus Oligophagous Xylem/± Indifferent Minor

Microdiprion pallipes Fall. Pinus Monophagous Needles/± Minor Major

Diprion pini L. Pinus Monophagous Needles/± Indifferent Major

Diprion butovitschi Hedq. Pinus Monophagous Needles/± Indifferent Minor

Diprion similis Htg. Pinus Monophagous Needles/± Indifferent Indifferent

Neodiprion sertifer Geoff. Pinus Monophagous Needles/± Major Major

Gilpinia socia Klug Pinus Monophagous Needles/± Indifferent Indifferent

Gilpinia laricis Jur. Pinus Monophagous Needles/± Indifferent Indifferent

Gilpinia virens Klug Pinus Monophagous Needles/± Indifferent Indifferent

Gilpinia pallida Klug. Pinus Monophagous Needles/± Indifferent Minor

Macrodiprion nemoralis Enslin Pinus Monophagous Needles/± Indifferent Indifferent

Lepidoptera

Exoteleia dodecella (L.) Pinus Monophagous Needles, buds/± Indifferent Minor

Archips oporana (L.) Pinus, Picea Oligophagous Needles/± Indifferent Minor

Blastehesthia posticana (Zett.) Pinus Monophagous Buds/± Indifferent

Blasthesthia turionella (L.) Pinus Monophagous Buds/± Minor Minor

Rhyacionia buoliana (D&S) Pinus Monophagous Shoots/± Major Major

Rhyacionia pinicolana (Doubl.) Pinus Monophagous Buds, shoots/± Indifferent

Rhyacionia pinivorana

(Lien. & Zell.)

Pinus Monophagous Buds/± Indifferent

Rhyacionia duplana (Hb.) Pinus Monophagous Shoots/± Indifferent Major

Retiniaresinella (L.) Pinus Monophagous Phloem/± Minor Minor

Dioryctria mutatella Fuchs Pinus Monophagous Needles, buds,

shoots/±

Indifferenta Minor

Dioryctria sylvestrella (Ratz.) Pinus, Picea Oligophagous Phloem/± Indifferent

Bupalus piniaria (L.) Pinus Oligophagous Needles/± Indifferent Major

Dendrolimus pini (L.) Pinus Oligophagous Needles/± Indifferent Minor

Hyloicus pinastri (L.) Pinus Oligophagous Needles/± Indifferent Indifferent

Orgyia antiqua (L.) Pinus, Picea Polyphagous Needles/± Minor Minor

Calliteara pudibunda (L.) Fagus Polyphagous Needles/± Indifferent Minor

Melanchra pisi (L.) Herbs Herbs Polyphagous Needles/± Minor Minor

Panolis flammea (D&S) Pinus Oligophagous Needles/± Indifferent Major

Actebia fennica (Tauscher) Herbs Polyphagous Needles/± Major Minor

Diptera

Thecodiplosis brachyntera Schwg. Pinus Oligophagous Needles/± Minor Major

Contarinia Pinus Oligophagous Needles/± Minor Major

aPest status refers to the degree of damage occurring lodgepole and Scots pine in the Nordic countries.

bMonophagous, i.e. feeding on species within one genus; ophagous, i.e. feeding on Pinus and Picea; oligophagous, i.e. feeding on Pinaceae; polyphagous, i.e.

feeding on ceae and deciduous trees and bushes/herbs.

114 AÊ . LindeloÈw, C. BjoÈrkman / Forest Ecology and Management 141 (2001) 107±116

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